1. Field of the Invention
The present invention relates to a continuously variable valve timing device for a vehicle, and more particularly, to an intermediate lock pin (ILP) type variable valve timing unit for a vehicle and a continuously variable valve timing device using the same, which can improve an intake pumping efficiency to improve the fuel economy.
2. Description of Prior Art
In general, a continuously variable valve timing device is a system that continuously changes the opening/closing time of a valve by changing the phase of a cam shaft in accordance with the engine revolution and load of a vehicle.
A conventional continuously variable valve timing device 101, as illustrated in FIG. 10, briefly includes a crank angle sensor sensing the rotation angle of a crank shaft, a cam angle sensor sensing the rotation angle of a cam shaft 104, a variable valve timing unit 150 connected to one side of the cam shaft 104 via a timing belt to advance or retard the cam shaft 104, and an engine control unit (ECU) controlling an oil control valve 108 to supply oil to an advance chamber 111a or a retard chamber 111b of the variable valve timing unit 150 based on signals from the crank angle sensor and the cam angle sensor.
The variable valve timing unit 150 is composed of a stator 110 connected to the crank shaft via the timing belt so as to receive a rotating force of the crank shaft, and a vane-shaped rotor 120 engaged in a body with the cam shaft 104 to rotate relatively to the stator 110.
In the stator 110, a chamber 111, which is divided into the advance chamber 111a and the retard chamber 111b by the rotor 120, is formed. If oil is supplied to the advance chamber 111a through the oil control valve 108, a phase difference occurs between the rotor 120 and the stator 110 to rotate the cam shaft 104, and thus the timing of the valve is changed.
Naturally, if oil flows into the retard chamber 111b through the oil control valve 108, a phase difference in an opposite direction to that of the above-described phase difference occurs between the rotor 120 and the stator 110 to loosen the timing of the valve.
A lock pin 131 is formed on the rotor 120 so that the rotor 120 is locked into the stator 110 when an engine stops working, and a pin locking part, into which the lock pin 131 is locked, is formed on the stator 110.
Recently, in order to prevent fuel economy from being lowered due to deterioration of the intake pumping efficiency of the variable valve timing device 101, developments for application of an intermediate lock pin (ILP) system to an intake-side variable valve timing unit have been made.
The ILP type variable valve timing device increases a retard region by 20° in comparison to a general variable valve timing device 101 by changing the time when the lock pin 131 is locked into the pin locking part, and thus the intake pumping efficiency is heightened to improve the fuel economy.
Here, in the case of adopting the ILP type oil control valve that supplies or intercepts oil to the chamber 111 in order to release or maintain the locking between the lock pin 131 and the pin locking part, there is a need for a structure for mounting the ILP type oil control valve thereon within a range where the layout of an engine room is not changed.
Also, in the conventional ILP type variable valve timing device, the lock pin 131 may not be properly locked into the pin locking part when the engine stops working.
Accordingly, if the engine is re-started in a state where the lock pin 131 is not properly locked into the pin locking part, the rotor 120 may bump against the stator 110 to be damaged with noise occurrence.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.